Effect of Post Annealing Process on Electrical and Magnetic Properties of Nd0.7Sr0.3MnO3 Thin Films

Nd0.7Sr0.3MnO3 thin films were deposited on (001) Al2O3 substrate by using rf-magnetron sputtering unit. The effect of post-annealing on the structural, electrical and magnetic properties are studied. These films exhibit orthorhombic structure and the compressive strain is found to decrease with increase in annealing temperature. Raman studies at room temperature show four well-resolved Raman peaks due to two Ag, B2g and B3g modes. One of the Raman lines is found to be sensitive to lattice strain and it disappears upon annealing the film at 900 °C. All the annealed films show double exchange ferromagnetic transition and the transition temperature increases upon increase in annealing temperature due to the reduced lattice strain and the improved oxygen stoichiometry. These films show metal-insulator transition and the resistivity data in the metallic region could be fitted to the empirical relation ρ = ρ0 + ρ2.5T2.5 while the resistivity in the semiconducting region could be fitted to variable range hopping model.